1. Field of the Invention
This invention relates to photosensitive compounds, more particularly, derivatives of halomethyl-1,3,5-triazines.
2. Discussion of the Prior Art
Compounds that decompose to generate free radicals (free radical generating agents) upon exposure to light are well known in the graphic arts. Organic halogen compounds, which are capable of generating free radicals such as a chlorine free radical or a bromine free radical upon exposure to light, have been widely used as photoinitiators in photopolymerizable compositions, as photoactivators in free radical photographic compositions, and as photoinitiators for reactions catalyzed by acids formed by light. The spectral sensitivity of these compositions may be broadened by the addition of sensitizers which, in essence, transfer their absorbed energy to the organic halogen compound. The use of such halogen compounds in photopolymerization processes and free radical photographic processes has been described in Kosar, Light-Sensitive Systems, J. Wiley & Sons (New York, 1965), pp. 180-181, 361-370.
Halomethyl-1,3,5-triazines are known to be initiators for a number of photochemical reactions. They are employed to produce free radicals for initiating polymerization or color changes and for initiating secondary reactions upon liberation of acid by the interaction of the free-radicals when hydrogen donors are present.
Examples of the use of the halomethyl-1,3,5-triazines in the free radical polymerization of acrylate monomers are described in U.S. Pat. No. 3,905,815; U.S. Pat. No. 3,617,288; U.S. Pat. No. 4,181,752; U.S. Pat. No. 4,391,687; U.S. Pat. No. 4,476,215; and DE 3,517,440 U.S. Pat. No. 3,779,778 discloses the photoinitiated acid catalyzed decomposition of pyranyl ether derivatives to produce photosolubilizable compositions useful as positive printing plates. Chromophore substituted styryl-1,3,5-triazines and their uses are disclosed in U.S. Pat. No. 3,987,037 and U.S. Pat. No. 3,954,475.
Radiation sensitive compositions containing bi- and polyaromatic substituted triazines are disclosed in U.S. Pat. No. 4,189,323.
Typical photopolymerization initiators for polymerizable ethylenically unsaturated compounds include benzil, benzoin, benzoin ethyl ether, Michler's ketone, anthraquinone, acridine, phenazine, benzophenone, etc. For example, the use of photoinitiators such as benzoin ethers are described in U.S. Pat. No 2,722,512; anthraquinones are described in U.S. Pat. No. 3,046,127; amino phenyl ketones and active ethylene or amino compounds are described in U.S. Pat. No. 3,661,588; and Michler's ketone and benzophenone are described in U.S. Pat. No. 3,682,641.
Mixed photoinitiators have been disclosed for use with polymerizable monomers. A very effective mixed initiator system has been Michler's ketone admixed with benzophenone, as described in U.S. Patent No. 3,682,641. 3-Keto-coumarins have been shown to be effective mixed initiators with Michler's ketone, as described in U.S. Patent No. 4,366,228. Halogenated organic photoinitiators such as carbon tetrabromide, etc, have been used as co-photoinitiators with diazonium salts, as described in U.S. Pat. No. 4,113,497. Likewise, 5-isoxazolones are effective co-photoinitiators when used with aromatic carbonyl compounds in the presence of halomethyl-1,3,5-triazines, as described in U.S. Pat. No. 4,254,432. Other examples of specific combinations of known photoinitiators are disclosed in U.S Pat. Nos. 3,814,607; 3,673,140; 3,326,710; 3,847,771; 3,427,161; 3,915,824, and 4,264,709.